for day trading tdameritrade is real good, their streamer app etc makes it real easy to go in and out and do tons of round trips all day at 9.99
im not a pro but here is some advice
a) only use your money to buy stocks when you start out, this way should a trade go the wrong way you are not forced to sell
b) stick to solid companies, to many times people get lurned into these silly stocks just because of their silly lottery style math. For example you see a tip online "buy crap.pk for 0.7 a share" you take out the calculator you figure out you can buy 500,000 shares and that means even if it goes up 5 cents you will make $25000, dont fall for this stuff, this is how people lose it all. Now do some make money? yeah, but some people also win the powerball.
c) do not become a price chaser, pre buy and presell, this means if say you look at MSFT and its at $30 a share and you say to yourself, when I see it at $29.50 ill buy, then pre set that in your account, or else you will be chasing stuff all day. Same once you own it and you say "ill sell it at 30.25" preset that, so it sells and you dont have your emotions playing with you and your money.
Its like if there would be a auto eject button in a casino that you can set that as soon as you make $500 it shoots you out of the place, more people will leave with money.
In order to make big money in the market short term you need big money, the more shares the less you need something to go up in order for you to make money.
Lets use a real example:
Joe has $10,000 in his account he buys citibank at 4.50, he can buy approx 2223 shares. if C goes up 5 cents he makes about 111 bucks, minus 20 bucks or so trading fees etc.
John has $50,000 he buys 11,115 shares, if citi goes up 5 cents he makes $555 dollars
BUT here is the kicker, john also can lose more but on a positive note dont even have to wait for it to go up to 5 cents even at 3 cents he can quickly get in and out
when you have to start waiting because you have little trading money you are setting yourself up for losses, in these days quick in and out gives you the best chace of winning
so
use your own money
use lots of money (obviously play and learn on little money, but be ok to lose a few K learning)
buy solid companies
pre buy and pre sell, take emotions out of things
a few other things to learn to make extra money (risky and for more advanced traders) learn about options
also learn about dividends, learn about ex dates and to quickly find high div paying stocks simply google high dividend paying stocks sites like
http://www.dividenddetective.com/big_dividend_list2.htm
it really takes money to make money in the market, thats why there are over 8000 hedge funds, they understand you must group together big cash and take big positions to see big returns.
The motivational stories about people who started with nothing and make millions leave to the old ladies.
Also remember, most people never buy stocks when the stock price is down, but history has shown only those who gamble at that time see the biggest return